Acid-doped polyaniline is finding an increasing level of interest as a solid electrolyte for capacitors and other electronics devices. The dopants are selected from a relatively small group of acids that enhance solubility in organic solvents with a low dielectric constant, e.g., a dielectric constant of less than about 17. Acid-doped polyaniline polymers are generally considered to have no practical solubility in solvents with a dielectric constant of greater than about 17. See U.S. Pat. No. 5,567,356. The most preferred polyaniline dopant is dinonyl naphthalene sulfonic acid (DNSA).
A commercially available solution contains DNSA-doped polyaniline in a solvent mixture containing xylene, ethylene glycol monobutyl ether. Unfortunately, this solvent system is characterized by toxicity and a suggested drying temperature of 150.degree.-200.degree. C. to remove the solvent from the acid-doped polymer. This high temperature is required to remove the xylene-based solvent from relatively porous surfaces as well as thin layers.
It would be useful to have a solvent system that exhibited low toxicity and a lower drying temperature than with xylene-based solvent systems.
It would be even more beneficial to have a solvent system that also had a relatively high boiling point. The higher boiling point would facilitate the use and handling of the solvent in a commercial setting.
Enhanced systems for forming polyaniline-based polymer films and coatings would be particularly useful in the manufacture of capacitors. In such articles, one or more coatings of electrically conductive polyaniline-based polymer can be used as a solid electrolyte between the dielectric oxide layer and the electrodes. It would be useful to have a polyaniline-based polymer dissolution system that did not pose the problems and limitations of the former xylene solvent systems.